Any chance you could add an option to start with a cave exit? I'm using a particular set of mods, specifically involving omnimatter and caves. When combined, omnimatter replaces all resources with omnite, then caves removes the omnite.

I could force caves mod to allow omnite spawning on the surface, but that would defeat the purpose of what I'm trying to accomplish, which is to have all resources come from the caves (through omnite). But without stone for the first cave entrance (and wood, because I also have islands mod..), I can't actually generate the caves I need to acquire more resources.

For now, I can code that in myself (by modifying an existing fast start mod), but it would still be nice to have the option within this mod. Please, and thank you!

EDIT: Nvm, doesn't matter. I had to drop this mod as it was reducing my fps/tps to 40, with consistent spikes right from the start of the game. Maybe it was just my mod list, but there were just too many script updates coming from this mod. Too bad

From what I understand, at the start of the game, it must do a large bit of cave generation ... So after about a minute or two, it shouldn't be doing much unless you have a extended radar mod.

I have also hacked this feature into my copy because I use a no hand crafting mod (BasicKit), and every second counts before first nightfall (actually also hacked it into the BasicKit mods startup items).

Interestingly, because the initial cave generation takes time, you won't be able to immediately place the entrance anyway, but in my case, I can chop wood during that time for fuel.

I was using Wormmus Config mod, which has a setting to change the initial map scan; I increased to the lowest setting above vanilla, which was 500. I was playing at 30 while it generated the map, so I just waited and let it finish, but after it was all done, I put down a cave entrance, walked into the cave, came back out, noticed it was still 40, and found Caves to have the highest script updates by far (15-16, compared to less than 1 for everything else)

Aside from the performance issues, the caves themselves were a lot more cramped than I had originally assumed, so I probably won't end up using this mod regardless

sorry, looks like the mod then won't work well in your case.
so the script updates you saw where still related to chunk generation; factorio generates chunks even further than the starting area, at a rate of 1 per second, which then triggers my cave generation. using normal settings this keeps up for around 32(?) minutes, after that the script updates from caves also would stop.
(however if you explore then, it would start generating again)

but basically i split the cave generation until it wasn't noticeable for me any longer ( in my case it runs with 60fps and it takes around 1.6 to 3 during generation, then goes to 0.2 when nothing happens). sorry, i don't think i could further split it so also in your case it runs smoothly as it might then not even be fast enough to catch up with the terrain generation.